The present invention relates to a method of loading a green tire, which is applied to a tire vulcanizer of a vulcanization system without a bladder, and an apparatus therefor.
The known tire vulcanizers are divided into two types: (1) a type in which a heating/pressurizing medium is introduced into a tire via a bladder when the tire is vulcanized, and (2) a bladderless type in which a heating/pressurizing medium is directly introduced into a tire when the tire is vulcanized. In the case of the latter tire vulcanizer of the bladderless type, when the diameter is increased to form the inner side of the bead portion including the bead toe portion of the tire, a ring-shaped pressing member is arranged in opposition to the bead ring portion of a tire mold.
In loading a green tire into a tire mold, an inside gripping type is desirable, in which the upper bead portion of the green tire is gripped from the inside from the viewpoint of tire quality.
A related art for a green tire loading apparatus of this inside gripping type is shown in FIGS. 5 to 10 (refer to Japanese Patent Provisional Publication No. 3-253310 (No. 253310/1991), if necessary).
In order to load a green tire, an upper mold 56 is raised to an upper opening position, and an upper bead portion 52 of the green tire 51 is gripped from the inside by means of inside gripping chucks 55 of an inside gripping loader 54 as shown in FIG. 5. Then, the green tire 51 is inserted between the upper mold 56 and a lower mold 61, and the center of the green tire 51 is aligned with the center position of the upper and lower molds 56 and 61.
Subsequently, as shown in FIG. 6, the inside gripping loader 54 is lowered, a lower bead portion 53 of the green tire 51 is aligned with a lower bead ring 64, and then the lower bead portion 53 is held and sealed by a lower bead holding portion 65 of a central mechanism 63. The inside gripping chucks 55 of the inside gripping loader 54 are removed from the upper bead portion 52 of the green tire 51. Then, the inside gripping loader 54 is raised and turned to retract from between the upper and lower molds 56 and 61.
Subsequently, as shown in FIG. 7, the upper mold 56 and an upper central mechanism 58 are lowered halfway so that the upper bead portion 52 of the green tire 51 comes in contact with an upper bead ring 59. Then, a low-pressure heating medium is supplied into the green tire 51 through supply pipes 70 and 71. Thereupon, the upper bead portion 52 of the green tire 51 is raised to fit the upper ring 59. Then, the upper bead portion 52 is held and sealed by an upper bead holding portion 60.
Subsequently, as shown in FIG. 8, the upper mold 56 is lowered, and the upper and lower molds are tightened with each other. Then, a high-pressure heating medium is supplied into the green tire 51 through supply pipes 70 and 71. This high-pressure heating medium is applied directly to the inner surface of the green tire 51 to accomplish vulcanization molding.
Upon completion of vulcanization molding, the holding of the upper bead portion 52 by means of the upper bead holding portion 60 is released, and the upper mold 56 and the upper central mechanism 58 are raised as shown in FIG. 9.
Subsequently, as shown in FIG. 10, an unloader 75 is inserted between the upper and lower molds 56 and 61, and the lower central mechanism 63 is raised to remove the vulcanized tire 76 from the lower mold 61. Then, the upper bead portion 52 of the vulcanized tire 76 is gripped from the inside by means of inside gripping chucks 77 of the unloader 75, and the holding of the lower bead portion 53 by the lower bead holding portion 65 is released. After that, the unloader 75 is turned to take the vulcanized tire 76 out of the tire vulcanizer.
However, the conventional green tire loading apparatus of the inside gripping type, shown in FIGS. 5 to 10, has the following problem: Since the temperature of the tire mold is approximately 200.degree. C., and the green tire material acquires a softening property upon being heated, the sidewall portion of the tire is heated, softened, and collapsed if the time between holding of the lower bead portion by the lower central mechanism and holding of the upper bead portion by the upper central mechanism is prolonged. As a result, the upper bead portion is misaligned, or erroneous holding occurs, so that both bead portions of the green tire are not inserted into the respective bead rings accurately and reliably.